Inertial micro sensors, accelerometers and angular rate sensors (micro gyros) are considered as one of the most promising and intensively researched application of the MEMS (micro-electrical mechanical systems) technology. Micro scale accelerometers (along with the pressure sensors) were probably among the first micromachined electromechanical devices and first publications on the subject can be traced back to seventies. Despite such a long history of micro accelerometers and large variety of reported concepts, the development of new architectures and operational principles of high performance yet low cost, compact and manufacturable accelerometers is highly desired and continues to attract researchers in both industry and academy. Although nowadays several MEMS-based inertial sensors were successfully commercialized and incorporated into consumer electronics products (mainly cell phones and computer games consoles) and in automotive industry (air bag crash sensors), micro accelerometers have not yet penetrated the market in the area of navigation, guidance and control applications, which impose much tougher requirements to the device performance.
The operational principle of micro scale accelerometers has an electromechanical nature and is based on sensing of a mechanical displacement/motion caused by acceleration. In contrast to micro gyroscopes where alternatives to electromechanical devices are possible (ring laser gyroscope (LRG) and fiber optic gyroscope (FOG)), current accelerometers are still dominated by electromechanical sensors, mainly because no challenging alternative technology has succeeded (except for quartz resonators, which are used in the lower-grade tactical applications). MEMS based accelerometers are either of the pendulous/displacement mass type without [1] or with closed-loop force re-balance control [2] or of the resonator type [3]. The mass displacement type devices are usually micro structures incorporating a proof mass suspended on elastic bending [4, 5] deformable elements.